A touch panel includes, as its sensor electrodes, transparent electrodes made of, for example, ITO (indium oxide). A touch panel for a large screen is, however, problematic in that its sensor electrodes made of ITO, have a large electric resistance, with the result of a decrease in the detection sensitivity of the touch panel.
In view of the above problem, there has been known a technique in which a touch panel includes, as its sensor electrodes, conductor lines in a net-like pattern to both maintain adequate light transmittance and decrease the electric resistance of the sensor electrodes.
Patent Literature 1 discloses forming sensor electrodes for a touch panel by (i) cutting a mesh pattern into different portions and (ii) separating those portions from each other in such a manner that the separation line is not conspicuous.
However, even in a case where sensor electrodes are formed as in Patent Literature 1, gaps are formed between adjacent sensor electrodes. This results in locally increased light transmittance. Thus, an electronic device including a combination of such a touch panel and a display device unfortunately lets a pattern be visually recognizable which pattern corresponds to the gaps, with the result of a decrease in the quality of a display image.
This indicates that in a case where a touch panel includes, as its sensor electrodes, conductor lines in a net-like pattern, those conductor lines are preferably in a uniform net-like pattern to maintain uniformity of light transmittance over the detection surface.
FIGS. 22 through 24 are each a view for describing a touch panel conductive film of Patent Literature 2. FIG. 22 is a plan view of a first conductive pattern in a first conductive film. FIG. 23 is a plan view of a second conductive pattern in a second conductive film. FIG. 24 is a plan view of a layered conductive film including the first conductive film and the second conductive film attached to each other.
As illustrated in FIG. 22, the first conductive film includes a first conductive section 514A having (i) first conductive patterns 520A each extending in the m direction of FIG. 22 and including thin metal lines 516 and (ii) first auxiliary patterns 540A arranged around the first conductive patterns 520A. The first conductive patterns 520A each include two or more first large grids 530A connected to each other. The first large grids 530A each include two or more small grids 550 combined with each other.
Further, as illustrated in FIG. 23, the second conductive film includes a second conductive section 514B having (i) second conductive patterns 520B each extending in the n direction of FIG. 23 and including thin metal lines 516 and (ii) second auxiliary patterns 540B arranged around the second conductive patterns 520B.
The second conductive patterns 520B each include two or more second large grids 530B connected to each other. The second large grids 530B each include two or more small grids 550 combined with each other.
In a case where the first conductive film 510A having the above configuration is attached to the second conductive film 510B having the above configuration so as to form a layered conductive film 500, the first auxiliary patterns 540A and the second auxiliary patterns 540B face each other in a plan view so as to form combination patterns 560. As a result, the layered conductive film 500 shows, as viewed from above, a large number of closely arranged small grids 550 as illustrated in FIG. 24. This arrangement causes the boundaries between the first large grids 530A and the second large grids 530B to be less conspicuous, with the result of improved viewability.
Patent Literature 3 similarly discloses that in a case where two conductive sheets are attached to each other, a large number of small grids are arranged in a plan view and that such an arrangement causes the boundaries between first large grids and second large grids to be less conspicuous.